Water intrusion into roof structures is a major concern. Leaking roofs cost homeowners, commercial property owners and property insurers hundreds of millions of dollars every year. Even the smallest leaks can cause expensive problems. Structural damage to metal or plywood roof decking and rafters due to rot and rust has been commonplace for decades. Black mold or toxic mold that grows in the wet roof and wall areas is known to cause severe physical problems for occupants as well as severe fiscal problems for builders and insurance companies.
Flat or low slope roofs are commonly used for commercial and multifamily building construction. While offering simplicity and limiting the building height, they are also the most difficult to seal and drain. Leaks occurring in flat or low slope roofs often appear on the inside of the building far from the point of origin.
New “green roof” systems include live plants placed in a garden-like setting on top of a roof structure. The garden roof areas help to control rainwater run-off, provide additional insulation, help reduce carbon dioxide and are aesthetically pleasing. While providing many benefits, a green roof system further complicates roof problems. A leak can be difficult to locate and can lead to the dig-up and destruction of large sections of the planted area.
There are several types of moisture detection sensors available for detecting water leaks. There are moisture detection tapes as described by Vokey et al. in Published PCT Application WO/05/10837 published Feb. 3, 2005. These detection tapes are suited for detecting water intrusion in selected areas of a building structure but are not well suited to roof applications.
In U.S. Pat. No. 6,175,310 (Gotti) issued Jan. 16, 2001 there is disclosed and arrangement which uses exposed conductors and hygroscopic material that is not suited to roof applications where metal decking and high humidity levels can cause electrical shorts and false alarms.
The tape as described by Vokey et. al. while being better suited to roof applications with both a protective covering over the conductors and no-hygroscopic components, does not provide for pinpointing the location of the water on the tape.
In U.S. Pat. No. 6,144,209 (Raymond) issued Nov. 7, 2000 there is provided an arrangement which describes a location method using a combination of specially designed insulated and detection conductors cabled together in a form helix. This design, while useful for detection and location of water on floor-like surfaces, can not be placed between the roof deck and waterproof membrane because of the large overall dimensions and the susceptibility of the cable design to crushing and shorting.
The moisture sensors may be placed directly under the waterproof membrane which is often torched-on resulting in high temperatures that the sensor must survive. None of the earlier designs address this issue.
Precise location of a resistive water fault along a pair of conductors is a problem if a connecting cable is used to join the sensing conductors to the monitoring unit. If the connecting cable conductors are of a different resistance per unit length or if the connecting cable is of an unknown length, then the measured distance to the water fault can be in error.